MOS field-effect transistors with very thin silicon dioxide based gate dielectrics may experience unacceptable gate leakage currents. Forming the gate dielectric from certain high-k dielectric materials, instead of silicon dioxide, can reduce gate leakage. When forming such a dielectric on a hydrophobic surface, it may be necessary to form a buffer layer (e.g., a thin layer of silicon dioxide or silicon oxynitride) on that surface prior to forming the dielectric on the buffer layer. The presence of a buffer layer between the substrate and the high-k dielectric may contribute to the overall electrical thickness of the gate/gate dielectric stack. As device gate lengths shrink (e.g., to lengths that are significantly less than 45 nm), it may be desirable to decrease that electrical thickness—which may be done by eliminating such a buffer layer.
Accordingly, there is a need for an improved process for making a semiconductor device that includes a high-k gate dielectric. There is a need for a process for forming such a device that does not include forming the high-k gate dielectric on a buffer layer that is formed on an underlying substrate. The method of the present invention provides such a process.